I am not sure what your plans are for Drupal 7, but I have a module (Search by Page Attachments, part of http://drupal.org/project/search_by_page) which depends on Search Files API. Since I just ported my module to Drupal 7, in the process I also ported the API portion of your module to Drupal 7.

I'll attach it in a zip file in a comment here in just a second. I didn't think making a patch file was all that useful.

I also didn't port the other modules in your project, just the API module.

Here's a new version. There was a small error in that other attachment.

This version passes all my attachment searching tests in Search by Page, so I'm reasonably certain that the helper API functionality works.

If you are not planning on releasing Search Files for Drupal 7, could you let me know (use my contact form or reply to this issue)?
I will in that case make plans to incorporate your API module into Search by Page. Thanks...

Good to know. The above zip file will get you part way there, at least.

I've also ported Search by Page Attachments to D7, which may also help you figure out the Field API, if your module needs that (since both upload and cck/filefield are subsumed in D7 by the File field, you might). Issue tracking progress of porting SBP to D7:#674070: Drupal 7 version of Search by Page